Lol even hot and fast that thing will take FOREVER to cook right. I'd estimate at least 20 hours even at the 275-300 range. Probably a whole 24 hours, or more, at a more traditional 225 range. I think it would almost have to be wrapped to keep the exterior from drying out too much.
On the other hand...the bone may help it cook, like the bone in a pork butt.
Toolbox, Where on this brisket is the bone located? Is it on the bottom under the flat? Or is it between the muscles?
Take some good pics of it. I am interested in seeing more of it before it is cooked and after it is trimmed. I'd like to get a good lay of the land, so to speak.